Permission cannot be mapped to a Target user or group during mailbox migration (4383550)

During a mailbox migration, the following error is reported:

Permission <user or group> cannot be mapped to a target user or group. Ensure that it is present in permissions' mapping.

As a result, folder-level permissions cannot be migrated to the target mailbox.

This issue occurs because the user or group that holds permissions on a source mailbox folder has not been successfully matched or migrated within the ODM.

For ODM to migrate folder-level permissions, it must be able to map the source user or group to a corresponding target user or group. If the account relationship does not exist in the ODM mapping table, the permission cannot be applied to the target mailbox.

1. Ensure that the affected user or group is included in an Account Discovery task.
2. Navigate to the Accounts tab and run a Match task for the affected object.
3. Verify that the account state shows Matched or Migrated in the ODM portal.
4. Rerun the Mail Migration task for the affected mailbox.

Once the account or group has been successfully matched, ODM will be able to resolve the permission holder and apply the folder-level permissions to the target mailbox.